Silicate-based glasses have been used as a basis for implantable compositions to support the bonding, growth or genesis of bone by fostering a supportive environment between the material and living, bone progenitor cells. It is widely recognized that successful bioactive glasses include calcium and silica in order to foster the needed supportive environment. Certain of these compositions are considered bioactive since they possess surfaces capable of fostering a calcium phosphate layer which, in turn, promotes bone bonding to the material. For example, U.S. Pat. No. 5,204,106 discloses a composition termed 45S5 glass which is composed of Na2O—CaO—P2O5—SiO2.
Day et al. U.S. Pat. No. 6,709,744 describes biocompatible materials for implantation which include borate-based glass or ceramic materials containing Na2O, CaO, P2O5, and B2O3. A specific example is a glass containing about 22.9 wt % Na2O, about 22.9 wt % CaO, about 5.6 wt % P2O5, and about 48.6 wt % B2O3. These materials contain a high CaO concentration to facilitate the formation of hydroxyapatite when exposed to phosphorus-containing fluids in-vivo or prior to implantation. These materials are in the form of loose particulates which are loosely packed, for example in a glass capillary tube for release into a host. Liang et al., Bioactive Borate Glass Scaffold for Bone Tissue Engineering, J. Non-Crystalline Solids 354 (2008), p. 1690-96; and Yao et al., In-Vitro Bioactive Characteristics of Borate-Based Glasses with Controllable Degradation Behavior, J. Am. Cer. Soc. 90 (2007), p. 303-306 also disclose borate-based glasses formulated with high CaO for the formation of hydroxyapatite. For example, the 0B, 1B, 2B, and 3B glasses described by Yao et al. contain 0, 17.7, 35.4, and 53 wt % borate.
There is a continuing need for biocompatible materials which promote rapid repair of mammalian tissue, and especially for enhancing vascularity.